Variable Resolution Uncertainty Expert System for Digital Bathymetry Database

ABSTRACT

System and method for estimating uncertainty by obtaining conditional probability densities of bathymetric uncertainty due to navigation error and bottom slope using a Monte Carlo technique, using the Monte Carlo results to train a Bayesian Network to provide the causal relationships of navigation error and bottom slope to bathymetric uncertainty, producing a histogram of bathymetric uncertainty from the Bayesian Network of the uncertainty for an area similar to the training set area, and estimating the uncertainty based on the histogram produced by the Bayesian Network.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority based on U.S. Provisional Patent Application No. 61/333,795 filed on May 12, 2010, the entirety of which is hereby incorporated by reference into the present application.

BACKGROUND

Devices and methods disclosed herein relate generally to data accuracy, and more specifically, to computing uncertainty for gridded data sets, for example, for historical gridded bathymetry data.

Estimates of uncertainty are becoming a requirement of oceanographic and acoustic models that use bathymetry. Further, bathymetry fusion algorithms that fuse disparate data sets into a single bathymetry surface can require uncertainty estimates of the input data. Still further, International Hydrographic Organization (IHO) standards prescribe that uncertainty be specified for all hydrographic and bathymetric products, with differing level of uncertainty tolerances depending on safety requirements. Ultimately, uncertainty in the bathymetry layer can be used for navigation safety for surface ships and submarine operations. Jakobsson et al., On the effect of random errors in gridded bathymetric compilations, Journal of Geophysical Research-Solid Earth, 107: Article 2358, 2002, estimate error on historic data sets based on Monte Carlo simulations where the two-dimensional position of the original data points, the soundings, are randomly perturbed using a normally distributed random number generator (RNG) illustrated in FIG. 1 (PRIOR ART), showing the established Monte Carlo procedure 100 as given originally by Jakobsson. FIG. 2 (PRIOR ART) shows a revised established Monte Carlo procedure 150, revised to match the notation and flow chart conventions used herein, where the number of soundings is J, the number of surveys is K, the horizontal and vertical uncertainties of the K^(th) survey are H_(K) and V_(K), the number of Monte Carlo simulations is N, and each loop is denoted by. For the K^(th) survey, the RNG perturbs the position data ˜

(0,V_(K) ²). The notation ˜

(0,V_(K) ²) means that the quantity follows a normal, or Gaussian, probability distribution with mean 0 and variance V_(K) ². If the output grids have I grid points, the gridded bathymetry surface is constructed 151 from a conventional minimum curvature spline interpolator for each n^(th) iteration, resulting in N different interpolated bathymetry surfaces 153. The gridded uncertainty estimate is the standard deviation 155 of the N surfaces. Navigation error and the bottom slope can predominantly influence the bathymetric uncertainty estimated from this method. This procedure can be computationally intensive and requires the use of original soundings data.

What are needed are a system and method that can estimate uncertainty in the interpolation/extrapolation of bathymetry data. What are further needed are a system and method that provide a statistically rigorous means for estimation of uncertainty for areas of the seafloor not covered by dedicated surveys or that fall in between point measurement locations, and that are computationally efficient and do not require the use of original soundings data.

SUMMARY

To address the above-stated needs, the present teachings provide a system and method for estimating uncertainty based on a Bayesian network (BN). According to Heckerman, A Tutorial on Learning with Bayesian Networks, MICROSOFT® Technical Report, MSR-TR-95-06, March 1995 (revised November 1996), “a Bayesian network is a graphical model that encodes probabilistic relationships among variables of interest.” The BN can accommodate missing data and can learn causal relationships, thus it can include probabilistic semantics. A BN can encode uncertain expert knowledge in expert systems.

The present teachings can provide a computationally efficient method for estimating bathymetric uncertainty for historical gridded bathymetry data sets. Uncertainty estimates are needed when data are stored in the Bathymetric Attributed Grid files, which require both bathymetry and uncertainty. An exemplary embodiment of the present teachings, the Digital Bathymetry Data Base, Variable Resolution Uncertainty Expert System (DUES), is based on a BN to provide a computationally efficient method for determining uncertainty in, for example, but not limited to, the Navy's Digital Bathymetric Data Base-Variable Resolution (DBDB-V). In the present teachings, the Monte Carlo technique can be used on representative sets of soundings data to obtain the conditional probability densities (CPDs) necessary for statistical inference. Causal relationships of navigation error and bottom slope to bathymetric uncertainty can be quantified by CPD's.

The computer-based system for estimating uncertainty can include, but is not limited to including, an automated conditional probability density processor computing conditional probability densities of bathymetric uncertainty due to navigation error and bottom slope using a Monte Carlo technique on representative sets of soundings data from the bathymetry database. The system can also include an automated BN trainer processor using the Monte Carlo results to train the BN to provide the causal relationships of navigation error and bottom slope to bathymetric uncertainty, producing a histogram of bathymetric uncertainty from the Bayesian Network of the uncertainty for an area similar to the training set area, and an automated uncertainty estimator estimating the uncertainty based on the histogram produced by the Bayesian Network, providing the uncertainty estimates to an upgraded bathymetry database.

The method for estimating uncertainty can include, but is not limited to including, the steps of obtaining conditional probability densities of bathymetric uncertainty due to navigation error and bottom slope using a Monte Carlo technique on representative sets of soundings data from the bathymetry database, using the Monte Carlo results to train the BN to provide the causal relationships of navigation error and bottom slope to bathymetric uncertainty, producing a histogram of bathymetric uncertainty from the Bayesian Network of the uncertainty for an area with similar bottom topography to the training set area, and estimating the uncertainty based on the histogram produced by the Bayesian Network. Similarity is quantified, for example, but not limited to, by statistical hypothesis testing of the distributions of the bottom slopes in one area versus the training area such that the null hypothesis cannot be rejected due to lack of evidence for rejection at a 99% percentile confidence level. The expert system of the present teachings is fundamentally different from established Monte Carlo procedure because statistical inference is used to estimate uncertainty whereas Monte Carlo uses standard deviation from simulations, and while Monte Carlo simulations can be used for training, Monte Carlo simulation is not the means by which the uncertainties are estimated. Further, original soundings are not required to estimate the uncertainty.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (PRIOR ART) is a graphical flowchart of the method of calculating uncertainty of the prior art;

FIG. 2 (PRIOR ART) is a flowchart of the method of calculating uncertainty of the prior art revised to indicate notation used herein;

FIG. 3 is a schematic block diagram of the creation and usage of CPTs generated from a Monte Carlo process;

FIG. 4 is a schematic block diagram of an exemplary uncertainty expert system;

FIG. 5 is a graphical user interface product of BN topology;

FIG. 6 is a table of horizontal error categories;

FIG. 7 is a schematic block diagram of the BN training process of the present embodiment;

FIG. 8 is a schematic block diagram of the present embodiment in the context of a system that queries navigation and bathymetry databases and populates a bathymetry database with uncertainties;

FIG. 9 is a flowchart of the process of Monte Carlo simulations of the present embodiment introduced in FIG. 7;

FIG. 10 is a flowchart of the process of calculating standard deviations of the present embodiment introduced in FIG. 7;

FIG. 11 is flowchart of the BN programming of the present embodiment introduced in FIG. 7; and

FIG. 12 is a schematic block diagram of the system of the present embodiment.

DETAILED DESCRIPTION

The problems set forth above as well as further and other problems are solved by the present teachings. These solutions and other advantages are achieved by the various embodiments of the teachings described herein below.

In the present embodiment, an established Monte Carlo technique can be used on representative sets of soundings data to obtain the CPD's necessary for the statistical inference. The BN can then produce a histogram of this uncertainty estimate for an area given the navigation errors used to survey the region and bottoms slopes that are present. A final estimate of uncertainty can be calculated by combining a variance estimate, such as, for example, but not limited to, mean plus one standard deviation or a quantile, from the BN's output histogram with the vertical error, V_(K), under the assumption of statistical independence between the two. The statistic can be user-supplied.

Referring now to FIG. 3, a BN adaptation can exploit the similarity of how errors propagate. Nodes A, B, and C are parents 25 of child node Y 21, meaning that A, B and C collectively cause effect Y. In this case, conditional probability table (CPT) 23 was created (i.e. the BN was trained) from Monte Carlo simulations. Causal relationships between, for example, but not limited to, navigation error and bottom slope to bathymetric uncertainty can be defined. The Monte Carlo technique can be used on sample data to train the BN and generate CPDs. Conditional probabilities can link parent nodes (A, B, C, etc.) 25 to child node Y 21. CPT's 23 can store conditional probabilities. Parent nodes 25 are histograms of their variables. Child histogram is a weighted sum of the conditional probabilities.

Referring now to FIG. 4, the conceptual flow 200 of an exemplary uncertainty expert system is shown. Distribution of navigation errors 201 and bottom slope 203, both at the i^(th) output point, are supplied to Bayes network 33. The uncertainty component from navigation error and bottom slope is estimated for each i^(th) point on output grid 205 with x total points through statistical inference of Bayes network 33. Interpolated longitudes and latitudes are given by lon′ and lat′.

Referring now to FIGS. 5 and 6, BN topology is shown as displayed by, for example, but not limited to, NETICA® software graphical user interface (FIG. 5) for training a BN and tabulated horizontal error categories 31 (FIG. 7) are shown as used in an exemplary BN. The process for training a BN by the Monte Carlo technique can include, but is not limited to including, the steps of tabulating applicable data, for example, horizontal errors 35, performing the Monte Carlo procedure on error categories 31 (FIG. 6), creating a 2D histogram 36 of possible uncertainties for a CPT, and repeating for different training areas. Horizontal errors 35 (FIG. 5) follow navigation errors. Bottom gradient 39 (FIG. 5) and uncertainty estimate 41 (FIG. 5) nodes follow a logarithmic binning scheme.

Referring now to FIG. 7, a high level view of an exemplary BN training process is shown. The figure illustrates computation of the standard deviation as modified by the present teachings and use of these results to construct the CPTs for the BN. Shown is the process of assessing uncertainty and training a Bayes network from Monte Carlo simulations. The process includes, but is not limited to, the steps of perturbing 51 sounding positions “n” times, where there is a Gaussian distribution of perturbed positions and where horizontal/navigation positioning error is 1 s of the Gaussian perturbation, obtaining 53 the standard deviation of the “n” bathymetry layers, increasing horizontal error by a predefined step size and repeating, and creating 55 CPT of standard deviations with horizontal error and slope using bivariate histogram at the end of the simulations.

Referring now to FIG. 8, an exemplary implementation of the present teachings is shown in which the BN is integrated into larger system 300, for example, the DUES system. First, a region of interest for an uncertainty estimate is defined, followed by a query 303 of, for example, but not limited to, available navigation 301 and bathymetry data 305 for the area. The query can be made manually or automatically. In the present embodiment, metadata codes 307, which indicate survey era and platform used, are read from the navigation data 301 to obtain the types of navigation and sonar systems used for the track lines in the area. The fractional lengths of the track lines with like error, that is, errors in the same error category, are then calculated. The sums of all track lengths with a like error divided by the total of all track lengths become the weights for the horizontal error 309 node for BN 313. The present embodiment extracts bathymetry data 305 from the same area to obtain the magnitude of the bottom gradient and “real-bit” flags 311 at each grid point; the latter indicates if the grid point is calculated from actual soundings (real-bit flag=1) or if it is determined purely from interpolation (real-bit flag=0). The present embodiment loops through each grid point, assigns bottom gradient 315 to the appropriate bin of the BN's Bottom Gradient node, and extracts the resultant histogram. Calculation of a user-specified quantile (median, 68.7^(th) percentile, etc.) or other statistic (mean, mean plus one standard deviation, etc.) for this histogram provides the intermediate uncertainty 317. The final uncertainty estimate is obtained by first adding the square of the intermediate uncertainty 317 to the square of the vertical error estimate 319. The square root of the sum is then the final uncertainty estimate at that grid point if real-bit flag=1. If real-bit flag=0, the square root is multiplied by a user-defined coefficient to magnify the uncertainty estimate 317 to account for higher uncertainty in purely interpolated values. The present embodiment finally combines the gridded bathymetry 321 and uncertainty layers into database 325 used to populate 323, for example, an upgraded DBDB-V database. Vertical error 319 can be estimated from a large number of factors, including uncertainties of the sonar, sound speed profile, ship positioning vertically, ship pitch and roll, etc.

Referring now primarily to FIG. 9, a method 350 for Monte Carlo simulations 51 (FIG. 7) can include, but is not limited to including, the steps of calculating 351 a one-time non-perturbed bathymetry to be used for later calculations of bottom slope. For this unperturbed grid, matrix S0 355 holds the interpolated longitude (Lon′) and latitude (Lat′) and depths (Z0′) 353. The bold face means that the quantity is a vector or matrix. In the present embodiment, there are M different horizontal error categories for which the BN needs to be trained (loop 367). Method 350 can include the step of obtaining 369 the m^(th) horizontal error, and, for each m^(th) horizontal uncertainty H_(m) category (m=1, . . . , M), creating files 371, for example, but not limited to, in ASCII format, for the longitude, latitude, depth, and horizontal uncertainty H_(m) to be used as input files for the Monte Carlo simulations. In the present embodiment, for each category, there are N simulations (loop 361) in which the locations 373 of the sounding points (or gridded points acting as sounding points) are perturbed from the original position (in meters after conversion 365 to universal transverse mercator (UTM) projection and specification of a UTM origin in the grid) by amounts ΔX_(n) in the east-west direction and ΔY_(n) in the north-south direction, incrementing 363 i through each iteration of loop 367. Positional perturbations ˜N(0, H_(m)) are provided by Gaussian pseudorandom number generator. For each n^(th) simulation (n=1, . . . , N) (loop 359), method 350 can include the step of interpolating 377 the data points 375 to provide bathymetry surface, Z_(mn)′. Interpolated positions 379 are then converted from UTM to the interpolated longitude and latitude. The matrix S_(mn)′ is the vector of Lon′, Lat′, and Z_(mn)′. Method 350 can include the step of storing each S_(mn)′ to file 357, for example, but not limited to, an ASCII text file, with the navigation uncertainty category, m, and the Monte Carlo loop number, n, stored in the file name in file 357. The interpolation algorithm can be, but is not limited to being, a windowed linear smoothing technique documented by Plant et al., I. A., Analysis of the scale of errors in nearshore bathymetric data, Marine Geology, 191, pp. 71-86, 2002.

In the present embodiment, N=100 Monte Carlo iterations are performed for each m^(th) set of simulations; the set of one hundred Monte Carlo simulations are then repeated M times for each horizontal error category in FIG. 5 in order to fully populate the CPT of the BN. In the present embodiment, each sounding is assumed to have the same probability distribution of horizontal error so that a statistical distribution for bathymetric uncertainty for a range of horizontal errors can be obtained. The actual data are assumed to have the horizontal errors in order to associate horizontal errors and slope to an intermediate uncertainty.

Referring now to FIG. 10, after completion of the Monte Carlo simulations 51 (FIG. 7), method 400 for computing 53 (FIG. 7) the gridded standard deviation of the bathymetry can include the steps of, for each m^(th) horizontal uncertainty category (loop 403), obtaining 405 N Monte Carlo runs for horizontal error H_(i), and computing 411 σ_(m)′, at each i^(th) output grid point (loop 409) from the N bathymetry grids. Method 400 can also include the step of calculating 407 the gridded bottom slope from the unperturbed bathymetry (S₀) file 401 using standard methodologies, for example, but not limited to, those in Zhou and Liu, Error Analysis on Grid-Based Slope and Aspect Algorithms, Photogrammetric Engineering & Remote Sensing, Vol. 70, No. 8, pp. 957-962, August 2004, with UTM positions and linear extrapolation of the computational edges. Method 400 can include the step of storing the gridded standard deviation 417 and bottom slopes 413 to files 415, for example, but not limited to, ASCII files 419 which can contain the interpolated longitude, latitude, and bathymetry, the Monte Carlo standard deviation, and the slope, given by matrix E_(m).

Referring now to FIG. 11, method 450 for Bayes net training 55 (FIG. 7) can include, but is not limited to including, the step of, for each m horizontal error (loop 451), accessing 453 Monte Carlo uncertainties and bathymetric slopes from the standard deviation file 357 (FIG. 9) for the first horizontal error category, H_(i). Method 450 can include the step of computing 455, using logarithmic binning schemes for both the bottom slopes and bathymetry uncertainties, a bivariate histogram (i.e., three-dimensional histogram) using, for example, but not limited to, the “hist3” function of the MATLAB® Statistics Toolbox, with slopes (let there be g₁, . . . , g_(p) slope bins, given by vector g) and intermediate bathymetry uncertainty (let there be s₁, . . . , s_(q) uncertainty bins, given by vector s), respectively, indexing the row and column bins of the bivariate histogram. Method 450 can include the steps of, when m≦1 (loop 461), normalizing and writing 459 the histogram to file 463, for example, but not limited to, an ASCII file, incrementing 457 a PCT index, and repeating steps 451, 453, 455, and 459 for subsequent horizontal uncertainties 35 (FIG. 5). Method 450 can further include the step of, when m>1 (loop 461), appending 465 the resultant normalized bivariate histograms to file 463. Method 450 can still further include the step of opening 467 Bayesian network *.neta file 469 in a NETICA® GUI, and displaying the CPT for the “Uncertainty Estimate” node. The CPT can, for example, be copied from the ASCII file into a spreadsheet-like data display for the CPT in the GUI. The CPT can be already arranged to have the same stacked structure as the file 463.

Referring now to FIG. 12, system 500 for estimating uncertainty can include, but is not limited to including, conditional probability density processor 501 obtaining conditional probability densities 503 of bathymetric uncertainty due to navigation error and bottom slope using a Monte Carlo technique on representative sets of soundings data from bathymetry database 521. System 500 can also include BN trainer processor 505 using the Monte Carlo results to train BN 513 to provide the causal relationships of navigation error and bottom slope to bathymetric uncertainty, producing histogram 507 of bathymetric uncertainty from BN 513 of the uncertainty for an area similar to the training set area, and uncertainty estimator 509 estimating the uncertainty based on histogram 507 produced by BN 513, providing uncertainty estimates 517 to updated bathymetry database 519.

The present embodiment is directed, in part, to software for accomplishing the methods discussed herein, and computer readable media storing software for accomplishing these methods. The various modules described herein can be accomplished on the same CPU, or can be accomplished on different computers. In compliance with the statute, the present embodiment has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the present embodiment is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the present embodiment into effect.

Referring again primarily to FIGS. 4, 7, 8, 9, 10, and 11, methods 200, 250, 300, 350, 400, and 450 can be, in whole or in part, implemented electronically. Signals representing actions taken by elements of apparatus 500 (FIG. 12) and other disclosed embodiments can travel over at least one live communications network. Control and data information can be electronically executed and stored on at least one computer-readable medium. Components of the apparatus can be implemented to execute on at least one computer node in at least one live communications network. Common forms of a computer-readable medium can include, for example, but not be limited to, a floppy disk, a flexible disk, a hard disk, magnetic tape, or any other magnetic medium, a compact disk read only memory or any other optical medium, punched cards, paper tape, or any other physical medium with patterns of holes, a random access memory, a programmable read only memory, and erasable programmable read only memory (EPROM), a Flash EPROM, or any other memory chip or cartridge, or any other medium from which a computer can read. Further, the computer readable medium can contain graphs in any form including, but not limited to, Graphic Interchange Format (GIF), Joint Photographic Experts Group (JPEG), Portable Network Graphics (PNG), Scalable Vector Graphics (SVG), and Tagged Image File Format (TIFF).

Although the present teachings have been described with respect to various embodiments, it should be realized these teachings are also capable of a wide variety of further and other embodiments. 

1. A computer-implemented method for estimating uncertainty in a bathymetry database comprising the steps of: obtaining conditional probability densities of bathymetric uncertainty due to horizontal error and bottom slope using a Monte Carlo technique on representative sets of soundings data from the bathymetry database, the representative sets being associated with a training set area; training a Bayesian Network to provide causal relationships between the horizontal error and the bottom slope and the bathymetric uncertainty based on the conditional probability densities; creating a first histogram of the bathymetric uncertainty from the Bayesian Network for an area similar to the training set area; and estimating an uncertainty based on the first histogram.
 2. The method as in claim 1 wherein said step of estimating comprises computing a statistical quantity based on the histogram.
 3. The method as in claim 1 wherein said step of training the Bayesian Network comprises the steps of: (a) perturbing positions of the sounding data “n” times; (b) obtaining standard deviations of “n” bathymetry layers from the perturbed positions; (c) increasing the horizontal error by a predefined step size and repeating steps (a) and (b); and (d) creating a conditional probabilities table of the standard deviations.
 4. An automated method for providing uncertainty estimates to a bathymetry database comprising the steps of: defining a region of interest for an uncertainty estimate; accessing navigation data and bathymetry data for the region of interest; obtaining track lines in the region of interest based on the navigation data; calculating fractional lengths of the track lines with like errors; computing weights for a horizontal error node based on the sums of the track lengths with the like errors divided by the total of the track lengths; extracting bathymetry data from the region of interest to obtain the magnitude of the bottom gradient; assigning the bottom gradient to a bin of a bottom gradient node; providing the horizontal error node and the bottom gradient node to the Bayesian Network; extracting a histogram from the Bayesian Network based on the horizontal error node and the bottom gradient node; calculating an intermediate uncertainty based on a statistic of the histogram; calculating a final uncertainty estimate based on adding the square of the intermediate uncertainty to the square of a vertical error estimate and computing either the square root of the sum or the square root multiplied by a pre-selected magnification coefficient to account for higher uncertainty in purely interpolated values; and populating a bathymetry database with the bathymetry data and the final uncertainty estimate.
 5. The method as in claim 4 wherein the vertical error estimate comprises uncertainties of sonar, sound speed profile, ship positioning vertically, and ship pitch, roll, heave and draft.
 6. An automated system for estimating uncertainty in an electronic bathymetry database comprising the steps of: an automated conditional probability density processor obtaining conditional probability densities of bathymetric uncertainty due to navigation error and bottom slope using a Monte Carlo technique on representative sets of soundings data from the bathymetry database, the representative sets being associated with a training set area; an automated Bayesian Network trainer processor training a Bayesian Network to provide the causal relationships of the navigation error and the bottom slope to the bathymetric uncertainty based on the conditional probability densities, said trainer processor producing a histogram of the bathymetric uncertainty from the Bayesian Network for an area similar to the training set area; and an automated uncertainty estimator estimating an uncertainty based on the output histogram.
 7. The system as in claim 6 wherein said automated uncertainty estimator estimates the uncertainty based a statistical quantity from the output histogram.
 8. The system as in claim 6 wherein said an automated Bayesian Network trainer processor training (a) perturbs positions of the sounding data “n” times, (b) obtains standard deviations of “n” bathymetry layers from the perturbed positions, (c) increases the horizontal error by a predefined step size and repeats (a) and (b); and (d) creates a conditional probabilities table of the standard deviations.
 9. A computer software system comprising computer code stored on computer readable medium for estimating uncertainty in an electronic bathymetry database, said computer code executing the steps of: obtaining conditional probability densities of bathymetric uncertainty due to navigation error and bottom slope using a Monte Carlo technique on representative sets of soundings data from the bathymetry database, the representative sets being associated with a training set area; training a Bayesian Network to provide the causal relationships of the navigation error and the bottom slope to bathymetric uncertainty based on the conditional probability densities; producing a histogram of the bathymetric uncertainty from the Bayesian Network for an area similar to the training set area; and estimating an uncertainty based on the histogram.
 10. The computer system as in claim 9 wherein said step of estimating comprises computing a statistical quantity based on the histogram.
 11. The computer system as in claim 9 wherein said computer code executes the steps of: (a) perturbing positions of the sounding data “n” times; (b) obtaining standard deviations of “n” bathymetry layers from the perturbed positions; (c) increasing the horizontal error by a predefined step size and repeating steps (a) and (b); and (d) creating a conditional probabilities table of the standard deviations.
 12. A computer system for providing uncertainty estimates to a bathymetry database comprising: a bathymetry database having navigation error data and bathymetry data for a region of interest; a Bayesian Network trainer processor obtaining track lines in the region of interest based on the navigation data, calculating fractional lengths of the track lines with like errors, computing weights for a horizontal error node based on the sums of the track lengths with the like errors divided by the total of the track lengths, extracting bathymetry data from the region of interest to obtain the magnitude of the bottom gradient, assigning the bottom gradient to a bin of a bottom gradient node, and providing the horizontal error node and the bottom gradient node to the Bayesian Network, the Bayesian Network providing a histogram based on the horizontal error node and the bottom gradient node; and an uncertainty estimator calculating an intermediate uncertainty based on a statistic of the histogram, calculating a final uncertainty estimate based on adding the square of the intermediate uncertainty to the square of a vertical error estimate and computing either the square root of the sum or the square root multiplied by a pre-selected magnification coefficient to account for higher uncertainty in purely interpolated values, and populating a bathymetry database with the bathymetry data and the final uncertainty estimate.
 13. The computer system as in claim 12 wherein the vertical error estimate comprises uncertainties of sonar, sound speed profile, ship positioning vertically, and ship pitch, roll, heave and draft.
 14. A computer software system comprising computer code stored on computer readable media for providing uncertainty estimates to a bathymetry database, said computer code executing the steps of: defining a region of interest for an uncertainty estimate; accessing navigation data and bathymetry data for the region of interest; obtaining track lines in the region of interest based on the navigation data; calculating fractional lengths of the track lines with like errors; computing weights for a horizontal error node based on the sums of the track lengths with the like errors divided by the total of the track lengths; extracting bathymetry data from the region of interest to obtain the magnitude of the bottom gradient; assigning the bottom gradient to a bin of a bottom gradient node; providing the horizontal error node and the bottom gradient node to the Bayesian Network; extracting a histogram from the Bayesian Network based on the horizontal error node and the bottom gradient node; calculating an intermediate uncertainty based on a statistic of the histogram; calculating a final uncertainty estimate based on adding the square of the intermediate uncertainty to the square of a vertical error estimate and computing either the square root of the sum or the square root multiplied by a pre-selected magnification coefficient to account for higher uncertainty in purely interpolated values; and populating a bathymetry database with the bathymetry data and the final uncertainty estimate.
 15. The computer software system as in claim 14 wherein the vertical error estimate comprises uncertainties of sonar, sound speed profile, ship positioning vertically, and ship pitch, roll, heave and draft. 